The first known life insurance contract was written in 1536 on the life of a British merchant, William Gybbons, for a term of one year. Gybbons died shortly before the policy was to expire, but the insurers refused the claim. They held that that Gybbons had indeed survived "twelve months" - twelve lunar months (of 28 days). The insurers were taken to court and ordered to pay.

Chapter 7, The Battle II, p. 112 - The Invisible Bankers, Everything The Insurance Industry Never Wanted You To Know (1982)